#include <iostream>
using namespace std;
#include <stack>
#include <queue>
void test()
{
	stack<int> st;
	st.push(1);
	st.push(2);
	st.push(3);
	st.push(4);

	while (!st.empty())
	{
		cout << st.top() << " ";
		st.pop();
	}
	cout << endl;
}

void test_queue1()
{
	queue<int> q;
	q.push(1);
	q.push(2);

	cout << q.front() << " ";
	q.pop();

	q.push(3);
	q.push(4);

	while (!q.empty())
	{
		cout << q.front() << " ";
		q.pop();
	}
	cout << endl;
}
int main()
{
	//test();
	test_queue1();
	return 0;
}